Safety braking device and a braking system comprising such device

ABSTRACT

The present invention mainly relates to an improved-safety braking device, intended for reducing the injury risks concerning the driver, owing to the brake pedal if a collision happens, in particular a front impact and, more particularly, the invention deals with an electrohydraulic braking device having a variable hydraulic reaction. 
     A braking device according to the present invention comprises a master cylinder ( 1 ) fitted with a pedal-feeling simulation cartridge ( 3 ), said master cylinder ( 1 ) being actuated by an actuating rod ( 11 ) connected to a brake pedal ( 12 ), said cartridge ( 3 ) comprising a resilient means ( 29 ) and compression means ( 38 ) for the resilient means ( 29 ). These compression means ( 38 ) can be actuated by a computer ( 81 ) on the detection of an injury risk concerning the driver&#39;s legs, so as to reduce the compression rate of the resilient means ( 29 ).

This invention mainly relates to an improved-safety braking device,intended for reducing the injury risks concerning the driver, owing tothe brake pedal if a collision happens, in particular a front impactand, more particularly, the invention deals with an electrohydraulicbraking device having a variable hydraulic reaction.

Electrohydraulic braking systems of a known type comprise a mastercylinder, actuated by an actuating rod connected to a brake pedal, atleast one hydraulic pump supplying the brakes with hydraulic fluid, thuspermitting the operation of the brakes, and a computer controlling thedelivery of brake fluid to the brakes mounted at the wheels. In a normaloperating situation, the master cylinder is not used for actuating thebrakes, but merely for reproducing the braking feeling at the brakepedal, i.e. the hydraulic-circuit reaction which the driver wouldactually feel if the braking operation were taken charge of by aconventional hydraulic braking circuit. The braking operation takesplace through the actuation of the hydraulic pump, which delivers brakefluid to the brakes following the detection of the driver's will toapply the brakes, and the solenoid valves stop interconnecting themaster cylinder and the brakes. The detection of the will to apply thebrakes involves various sensors, for instance a travel sensor, disposedat the brake pedal. The simulation of the usual braking feeling (themechanical reaction of the circuit) is reproduced using a cartridge,communicating with the primary chamber of the master cylinder andcomprising resilient means, simulating the brake fluid absorption by thebraking circuit.

The reliability of such braking systems is further improved through theuse of the master cylinder as a source of pressure brake fluid for thebrakes, if the computer or the hydraulic pump happens to be unavailable.

In the case of an impact on the front part of the vehicle, thedeformation of the engine compartment of the vehicle is most likely tocause the recoil of the master cylinder towards the passenger space and,with it, of the actuating rod and of the brake pedal, and to injure thedriver, in particular his legs.

On a collision, if the driver's foot is on the brake pedal, and even ifthe pedal does not move back, his foot may be fractured just because ofthe mechanical reaction of the braking circuit.

In an attempt to reduce such injury risks, braking devices are known,which cause the exhaust of brake fluid to the outside of the circuit,thus leading to a pressure drop in the braking circuit, and enabling thebrake pedal to penetrate into the master cylinder without any reaction.Yet, owing to the flammability of brake fluid, such a fluid occurrenceinside the engine compartment may be quite hazardous and cause much moreserious damages than those resulting from a back motion of the brakepedal.

Besides, another drawback of this kind of device is that a brakingaction is no longer possible.

Moreover, the repair of such devices after an impact is very expensive.

Therefore, it is an object of the present invention to provide animproved-safety braking device, so as to reduce injury risks owing tothe brake pedal on a collision.

Another object of this invention consists in providing animproved-safety braking device with a simple and inexpensive designcompared with the existing devices.

It is also an object of the present invention to provide animproved-safety electrohydraulic braking device, which may be easilyadaptable to current electrohydraulic braking devices.

These objects are achieved, in accordance with this invention, by abraking device comprising a brake pedal, which is connected to a atleast partially hydraulic generator of a braking feeling at the pedal,and having a variable absorption, a system for the detection of thedriver's will to apply the brakes, such system being taken charge of bya computer, and a system for the detection of an injury risk, suchinjury-risk detecting system informing the computer of such an injuryrisk, and said computer controlling the absorption variation of thepedal-feeling simulation generator.

In other terms, the generator is fitted with means for a at leastpartial release of the resilient means simulating the pedal feeling,such means being actuated when an injury risk concerning the driver isdetected and bringing about an absorption reduction of the brakingdevice, thus reducing the injury risks concerning the driver.

An advantage of this invention lies in that its implementation does notrequire extensive alterations to a current device and in that it doesnot require much room either.

Advantageously too, the present invention makes it possible to usecurrent computers, for instance the one used for triggering theinflation of the air bags.

Therefore, a subject matter of the present invention is a brakingdevice, comprising an actuating rod connected by a first longitudinalend to a brake pedal, a pedal-feeling simulation cartridge connected toa second longitudinal end of said actuating rod, said cartridgecomprising a resilient means, and compression means for said resilientmeans, characterised in that the compression rate of the resilient meansis determined by the compression means and is capable of varying if aninjury risk concerning the driver is detected.

More particularly, the present invention deals with a braking deviceintended for a braking system, comprising an actuating rod connected bya first longitudinal end to a brake pedal, a pedal-feeling simulationcartridge having a longitudinal axis and isolated from the brakingsystem in a normal operating state, said cartridge comprising aresilient means, which may be elastically deformed by a pressurehydraulic fluid so as to transmit the reaction of a hydraulic brakingcircuit to the brake pedal through a second longitudinal end of thecontrol rod, said reaction being predetermined by a compression rate ofthe elastically-deformable means, and said compression rate being set bycompression means, characterised in that said device comprises means forvarying the compression rate of the resilient means of said cartridge onorder, on the detection of an injury risk concerning the driver, throughan action exerted on the compression means.

Another subject matter of the present invention is a braking device,characterised in that the compression rate of the resilient means isdetermined by the axial position of the compression means along theaxis.

According to another aspect, this invention provides a braking device,characterised in that the axial position of the compression means isdetermined by axial-indexing means.

Another subject matter still of the present invention is a brakingdevice, characterised in that said compression means comprise a bearingelement resting on the resilient means.

According to another aspect of the invention, a braking device ischaracterised in that the bearing element comprises a stem, capable ofsliding inside the cartridge on the detection of an injury riskconcerning the driver.

Another subject matter still of the present invention is a brakingdevice, characterised in that the bearing element is held in positionthrough the clamping of a first longitudinal end of the stem of thebearing element by the axial-indexing means.

The present invention also deals with a braking device, characterised inthat the bearing element has, at a second longitudinal end facing awayfrom the first end, rigidly locked with the cartridge, a support-formingcup for the resilient means.

According to another aspect of the invention, a braking device ischaracterised in that the axial-indexing means for the bearing elementcomprise a pyrotechnic charge, which may be triggered on the detectionof an injury risk concerning the driver, so has to let the stem of thebearing element slide freely relative to the cartridge.

Another subject matter still of the present invention is a brakingdevice, characterised in that the axial-indexing means for the bearingelement comprise electromagnetic means, controllable on the detection ofan injury risk concerning the driver so as to let the stem of thebearing element slide freely relative to the cartridge.

Another subject of the invention is a braking device, characterised inthat the resilient means is made up of an elastomer.

This invention also deals with a braking device, characterised in thatit is an electrohydraulic braking device comprising a master cylinder,actuated by the actuating rod and connected to the pedal-feelingsimulation cartridge, and wherein, in a normal operating state, theinner space of said master cylinder communicates with the inner space ofsaid cartridge whereas, in a deteriorated operating state, said mastercylinder is capable of actuating the brakes directly.

According to another aspect of the invention, a braking system,comprising a control system for the brakes disposed at the wheels, and adetection system for an injury risk concerning the driver, ischaracterised in that it comprises a braking device according to thepresent invention.

This invention also deals with a braking system, characterised in thatit comprises a braking device wherein, in a deteriorated operatingstate, the inner space of said master cylinder is connected to thebrakes disposed at the vehicle wheels, by the opening of first solenoidvalves, at least one computer controlling the opening and closing of thesolenoid valves, at least one hydraulic pump connected to the brakesthrough second solenoid valves, and at least one sensor for thedetection of an injury risk concerning the driver, characterised in thatthe axial-indexing means are controlled by the computer following thedetection of an injury risk concerning the driver.

Another subject of the invention is a braking system, characterised inthat, on the detection of an injury risk concerning the driver, thecomputer commands the pump to deliver brake fluid to the brakes.

Another subject matter still of the invention is a braking system,characterised in that the detection of an injury risk concerning thedriver results from the detection of a deceleration value, which isgreater than a predetermined value.

The present invention also deals with an electrohydraulic brakingsystem, characterised in that it comprises connection means for adecelerometer of at least one air bag, wherein the detection by saiddecelerometer of a deceleration value, which is greater than apredetermined value, controls the reduction of the compression rate ofthe resilient means.

Other features and advantages of the present invention will be apparentfrom the following detailed description, by way of example and by nomeans as a limitation, when taken in conjunction with the accompanyingdrawings, in which

FIG. 1 is a longitudinal sectional view of a master cylinder fitted witha pedal-feeling simulation cartridge according to this invention, andshowing two loading rates for the resilient means inside the cartridge;and

FIG. 2 is a functional diagram of an electrohydraulic braking circuitaccording to the present invention, comprising a master cylinder as perFIG. 1.

As a rule, in these drawings, the front part or the forward directionand the rear part or the rearward direction are the left-hand side andthe right-hand side respectively.

FIG. 1 shows a master cylinder 1 having an axis X, which is fitted witha pedal-feeling simulation cartridge 3 according to this invention. Themaster cylinder comprises a primary chamber 5, in which a first and asecond hydraulic pistons 7 and 9 are fitted for a leakproof slidingtravel, and define primary and secondary hydraulic circuits, connectedto the brakes. In a normal operating situation, solenoid valves stop theinterconnection of the primary and secondary circuits and the brakes. Atrest, and in accordance with the regulations in force, these solenoidvalves must be open.

The primary hydraulic circuit alone will be described, because thestructure of the secondary hydraulic circuit looks almost like that ofthe primary hydraulic circuit. The piston 7 comprises a body 8,exhibiting, at a first end facing rearwards, a substantially cone-shapedreceiving cavity for an actuating rod 11, fitted without any clearanceusing holding means 13, the connecting rod 11 being connected to a brakepedal 12. The body is also provided, at a second end facing forwards,with a substantially cylindrical sleeve 14, fitted for a leakproofsliding motion inside the chamber 5. The tightness is ensured by sealingmeans 15, for instance a lip seal fitted stationarily in the body of themaster cylinder. The periphery of the sleeve 14 is provided with radialpassages 17, advantageously at regular intervals, for the resupply ofthe primary hydraulic circuit with brake fluid from a tank 16. When thepiston moves in the forward direction in the chamber 5, the passages 17are closed by a lip seal 21, advantageously disposed stationarily insidean annular groove made in the body of the master cylinder.

There is nothing to prevent either the stationary fitting of the lipseal 21 in an insert, which would be fixed in position relative to thebody of the master cylinder, or the fitting of the seal 21 between ashoulder, formed in the inner periphery of the primary chamber 5 of themaster cylinder, and e.g. an inserted ring.

A return spring 23 is compressively fitted in a pressure chamber 19,defined by the pistons 7 and 9, that is between the rear face of thehydraulic piston 9 and the end wall of the sleeve 14 of the hydraulicpiston 7.

The pedal-feeling simulation cartridge 3 has a substantially cylindricalshape with an axis X′ and, in the embodiment illustrated in FIG. 1, theaxis X′ of the cartridge 3 is advantageously parallel to the axis X ofthe master cylinder 1, but such cartridge 3 may be arranged in anotherdirection as well. The cartridge comprises a blind bore 28 with an axisX′, consisting of three portions, the diameters of which are decreasingfrom the front part to the rear part, whereas the transitions of theseportions are shoulders 30, 33. The bore 28 accommodates a resilientmeans 29 and, in the illustrated example, such resilient means exhibitsthe shape of a sleeve having the axis X′. This sleeve comprises at afirst end, facing rearwards, a cap 34 looking like a comparativelysmaller-diameter sleeve while, at its second end facing forwards, i.e.in the opposite direction to that of the first end, it comprises a seat36. The resilient means 29 is may be made up of rubber.

The possibility of manufacturing the resilient means 29 from varioussprings with various loading rates, for instance with variable pitches,and from rubber elements, may be contemplated just as well.

The resilient means 29 is compressively fitted in the bore 28 usingcompression means 38, which comprise a bearing element 39 rigidly lockedwith the cartridge. The resilient means 29 is compressively disposedbetween the bearing element 39 and a plug 31, sealing the open end ofthe blind bore 28 using e.g. a O ring (not shown). In an advantageousmanner, the plug 31 fixes the resilient means 29 in place inside thecartridge 3, in that the seat 36 of the resilient means 29 is grippedbetween the rear face of the plug 31 and the shoulder 33 of the bore 28.The compression rate N, or the loading rate, of the resilient means 29is determined according to the pedal feeling to be given to the driver,which means that the greater the compression rate, the harder thecircuit reaction. In a normal braking situation, the compression rate Namounts to N1, as shown in FIG. 1 in the lower part of the illustratedcartridge 3.

Advantageously, the plug 31 is threaded so as to be screwed in the frontportion of the bore 28, provided with an internal thread cooperatingwith the plug thread.

The plug 31 might also be secured in the cartridge body using glue orany other fixing means.

The compression means 38 comprise axial-indexing means 44 for thepositioning of the bearing element 39 and for the adjustment of theloading rate of the resilient means 29.

In the example as illustrated, the bearing element 39 comprises a stem43 having an axis X′ and capable, on a collision, of sliding in thecartridge 3 in the outward direction. The stem 43 is fitted, at a firstend facing forwards, with a cup 40 accommodating the closed end of thecap 34 of the resilient means 29 and translationally-locked relative tothe cartridge 3, by a second end 41 facing away from said first end,through the axial-indexing means 44, most advantageously by clamping.The means 44 can be controlled by a computer so as to change the axialindexing of the bearing element 39, thus resulting in a variation of theloading rate as regards the resilient means 29.

Thanks to the indexing means 44, the bearing element 39 may take, forinstance, two axial positions, namely a first position in which theresilient means 29 is compressed to a first loading rate N1 in a normaloperating situation, and a second position in which the loading rate ofthe resilient means 29 is reduced to a second rate N2 so as to reducethe reaction of the hydraulic circuit, as shown in the upper part of thecartridge 3 represented in FIG. 1. The axial-indexing means comprise,for instance, a pyrotechnic charge, activated by a computer,advantageously the one controlling the air bag, and the triggering ofthe charge causes the rupture of the attachment of the end 41 of thestem 43 to the cartridge 3.

Of course, arrangements may be made to use indexing means 44 comprisingmechanical means, e.g. a rack device, or electromagnetic means,controlled by the computer, and readily reusable after a triggering.

The bore 28, and more particularly the inside of the resilient sleeve 29communicates with the chamber 19 by means of a radial passage 25provided in the body of the master cylinder, between the primary chamber5 and the inside of the cartridge 3, and by means of a passage 27extending between the rear portion of the hydraulic piston 9 and theinner peripheral surface of the chamber 5.

Contrary to the primary hydraulic circuit, the secondary hydrauliccircuit is not capable of being connected with the inside of thecartridge.

FIG. 2 shows a braking circuit, comprising the master cylinder accordingto this invention, in which the primary and secondary chambers areconnected, through the pipes 50 and 53, with the brakes 55, 57, 59 and61 at the wheels. The pipes are fitted with solenoid valves 63, 65capable of separating the master cylinder from the brakes. The brakingcircuit also comprises at least one hydraulic pump 67, advantageouslydriven by an electric motor 68, and communicating with the brakes 55,57, 59 and 61 through the pipes 71, 73, 75 and 77. Solenoid valves 80are capable of isolating the pumps 67, 69 from the brakes 55, 57, 59,61. The braking circuit also comprises an injury-risk detector (notshown), for instance the decelerometer of the air bag(s), and othersensors as well. A computer 81 receives data about the driver's will toapply the brakes, from the sensors, e.g. a travel sensor 82 for theactuating rod 11, and from the injury-risk detector, and the computercontrols the opening and the closing of the solenoid valves 63, 65, 80and the starting of the pumps 67, 69.

In a normal braking operation, some solenoid valves are closed, whichmeans that they no longer interconnect the primary circuit, thesecondary circuit and the brakes, with the result that the brake fluid,contained in the secondary circuit, is confined inside the secondaryhydraulic chamber, and that the secondary piston 9 does not slide in thechamber 5 any longer.

At rest, the solenoid valves 63, 65 are open and therefore, if adysfunctioning occurs in the electronic system, the primary andsecondary chambers of the master cylinder are communicating with eachother, which enables the master cylinder to supply brake fluid to thebrakes 71, 73, 75 and 77, quite conventionally.

The mode of operation of the electrohydraulic braking device accordingto this invention will be explained now, both in an normal brakingsituation and on the detection of an injury risk, the lattercorresponding e.g. to the detection, by the computer, of a decelerationspeed D, which is higher than a predetermined value V.

In a normal deceleration braking, i.e. when the deceleration speed D islower than the value V, the driver depresses the brake pedal, whichbrings about a forward travel of the actuating rod 11 and consequently asliding motion of the piston 7. The tank and the chamber 19 stopcommunicating through the passages 17 as soon as the lip of the seal 21covers the passages 17. The brake fluid is delivered to the cartridge 3through the passages 25, 27, and the resulting pressure rise deforms theresilient means 29 to the compression rate N1. The compressive stresses,applied to the resilient means 29, make it possible to reproduce thereaction of the hydraulic circuit or the feeling at the brake pedal,like that the driver would get when decelerating a vehicle equipped witha conventional hydraulic braking circuit.

Simultaneously, a sensor (not shown), e.g. a travel sensor, detects thetravel and the speed of motion of the actuating rod 11 and transmitsthese data to the computer, which commands the hydraulic pump(s) todeliver a determined brake fluid volume to the brakes, such brake fluidvolume being set as a function of the braking level the driver wants.

On a collision, when an injury-risk detector, e.g. a decelerometer 90 ofat least one air bag 91, measures a higher deceleration speed D than thepredetermined value V, these data are transmitted to the computer.

Two cases may arise, as follow:

-   -   The first case is that in which the driver's foot is on the        brake pedal when an injury risk is detected.

The computer commands, among others, the indexing means 44 to releasethe resilient means 29, by the disengagement of the stem 43 from thecartridge, with the result that the compression rate N of the resilientmeans becomes N2, N2 being lower than N1. Thus the resilient means 29 ispartly decompressed and the pressure both in the cartridge and in thechamber 5 is reduced, the effect of which being that the brake pedal mayoffer a weaker resistance to the driver's foot than that the driverwould feel if the resilient means 29 were normally compressed to therate N1. Therefore the brake pedal will cause the driver only veryslight hurts, if any at all.

-   -   The second case is that in which the driver's foot is not on the        brake pedal when an injury risk is detected.

The computer commands, among others, the indexing means 44 to releasethe resilient means 29; by the disengagement of the stem 43 from thecartridge 3, with the result that the resilient means 29 is partlydecompressed, and that the pressure both in the cartridge and in thechamber 5 is reduced. Therefore, the master cylinder may move, e.g.under the effect of the impact, relative to the actuating rod. As amatter of fact, because that the brake fluid pressure inside the mastercylinder is low, the master cylinder may move more easily relative tothe actuating rod. Accordingly a back motion of the brake pedal fartherinto the passenger space is limited, which means that the injury risksincurred are reduced as well.

Following an impact, the vehicle may happen to keep moving. Then, sincethe braking operation is independent of the pedal-feeling simulator, andif the brake control system is still functioning, provision may be madefor the brake control system to command, as soon as an injury-risk isdetected, the hydraulic pumps to deliver brake fluid to the brakes so asto bring the vehicle to a standstill.

Therefore the invention provides a braking device ensuring the driver animproved safety, and cooperating, in a simple and especiallyadvantageous way, with the braking system already installed in thevehicle.

The present device is quite advantageous as regards electrohydraulicbraking systems yet it is adaptable just as well to any other brakingsystem whatsoever comprising a pedal-feeling generating device.

The present invention concerns, more particularly, the motor carindustry.

And the present invention mainly applies to the design and manufacturingof braking systems for motor vehicles and, more especially, of brakingsystems for passenger cars.

1. A braking device intended for a braking system, comprising anactuating rod (11) connected by a first longitudinal end to a brakepedal (12), a pedal-feeling simulation cartridge (3) having alongitudinal axis (X′) and isolated from the braking system in a normaloperating state, said cartridge (3) comprising a resilient means (29),which may be elastically deformed by a pressure hydraulic fluid so as totransmit the reaction of a hydraulic braking circuit to the brake pedal(12) through a second longitudinal end of the control rod (11), saidreaction being predetermined by a compression rate of theelastically-deformable means (29), and said compression rate being setby compression means (38), characterised in that said device comprisesmeans for varying the compression rate of the resilient means of saidcartridge on order, on the detection of an injury risk concerning thedriver, through an action exerted on the compression means (38).
 2. Thebraking device according to claim 1, characterised in that thecompression rate of the resilient means (29) is determined by the axialposition of the compression means (38) along the axis (X′).
 3. Thebraking device according to claim 2, characterised in that the axialposition of the compression means (38) is determined by axial-indexingmeans (44).
 4. The braking device according to claim 3, characterised inthat said compression means (38) comprise a bearing element (39) restingon the resilient means (29).
 5. The braking device according to claim 4,characterised in that the bearing element (39) comprises a stem (43),capable of sliding in the cartridge (3) on the detection of an injuryrisk concerning the driver.
 6. The braking device according to claim 5,characterised in that the bearing element (39) is held in positionthrough the clamping of a first longitudinal end (41) of the stem (43)of the bearing element (39) by the axial-indexing means (44).
 7. Thebraking device according to claim 6, characterised in that the bearingelement (39) has, at a second longitudinal end facing away from thefirst end (41), rigidly locked with the cartridge, a support-forming cup(40) for the resilient means (29).
 8. The braking device according toclaim 6, characterised in that the axial-indexing means (44) for thebearing element (39) comprise a pyrotechnic charge, which may betriggered on the detection of an injury risk concerning the driver, sohas to let the stem (43) of the bearing element (39) slide freelyrelative to the cartridge (3).
 9. The braking device according to claim6, characterised in that the axial-indexing means (44) for the bearingelement (39) comprise electromagnetic means, controllable on thedetection of an injury risk concerning the driver, so as to let the stem(43) of the bearing element (39) slide freely relative to the cartridge(3).
 10. The braking device according to claim 8, characterised in thatthe resilient means (29) is made up of an elastomer.
 11. The brakingdevice according to claim 10, characterised in that it is anelectrohydraulic braking device comprising a master cylinder (1),actuated by the actuating rod (11) and connected to the pedal-feelingsimulation cartridge (3), and wherein, in a normal operating state, theinner space of said master cylinder communicates with the inner space ofsaid cartridge (3) whereas, in a deteriorated operating state, saidmaster cylinder is capable of actuating the brakes directly.
 12. Thebraking device of claim 11 for use in a braking system having a controlsystem for the brakes disposed at the wheels, and a detection system foran injury risk concerning the driver.
 13. The braking device accordingto claim 12 wherein in a deteriorated operating state, the inner spaceof said master cylinder (1) is connected to the brakes (55, 57, 59, 61)disposed at the vehicle wheels, by the opening of first solenoid valves(63, 65), at least one computer (81) controlling the opening and theclosing of the solenoid valves (63, 65), at least one hydraulic pump(67) being connected to the brakes (55, 57, 59, 61) through secondsolenoid valves (80), and at least one sensor for the detection of aninjury risk, characterised in that the axial-indexing means (44) arecontrolled by the computer (81) following the detection of an injuryrisk concerning the driver.
 14. The braking device according to claim13, characterised in that, on the detection of an injury risk concerningthe driver, a computer (81) commands the pump (67, 69) to deliver brakefluid to the brakes (55, 57, 59, 61).
 15. The braking device accordingto claim 14, characterised in that the detection of an injury riskconcerning the driver results from the detection of a decelerationvalue, which is greater than a predetermined value.
 16. The brakingdevice system according to claim 15, characterised in that it comprisesconnection means for a decelerometer (90) of at least one air bag (91),wherein the detection by said decelerometer of a deceleration value,which is greater than a predetermined value, controls the reduction ofthe compression rate of the resilient means (29).